Question about dress codes

This will be my first trip to CSS and I want to make a reservation at the nice restaurant (cassinovo, I think it's called)...would slacks and a short sleeve button down be proper attire for a male or should I pack a sports jacket also?

We have been very disappointed in the lack of enforcement of the dress code at Cassanova the last two times we were at CSS. The majority of the guests take the dress code seriously, but there have been a few young men that showed up in shorts and jeans...and they're allowed to dine. Why are they allowed in when the rest of us take the time to pack properly? Not sure, but it is frustrating.